A fast-forward mode or a reverse mode is known as a trick mode among reproduction modes of digital video data. The Patent Citations 1 and 2 disclose techniques which provide higher quality images using the trick mode reproduction process.
The Patent Citation 1 discloses a method whereby separate trick play data that is only for reproduction in a fast-forward mode and in a fast-reverse mode is prepared in addition to normal play data to enable the switching of signals to be read-out depending on the reproduction modes requested from a terminal. The trick play data for fast-forward reproduction at n-times play speed has frame numbers of 1, n+1, 2n+1 . . . . Such a method enables a quick switch from a normal mode to a trick mode and vice versa, and, shortens the time for reading-out the data.
The Patent Citation 2 discloses an apparatus for reproducing encoded video data utilizing the Motion Picture Coding Experts Group (MPEG) video compression protocol. This apparatus reproduces encoded video data in a fast-forward mode at n-times play speed by only decoding I-pictures and P-pictures when the frame interval of anchor frames is n (n=2, 3). This apparatus also performs fast-forward playback at twice the play speed by outputting the same frame twice for every two frames when the frame interval of the anchor frames equals three. The frame interval of the anchor frames is a frame interval between I-picture and P-picture or a frame interval between P-pictures.    Patent Citation 1: Patent H06-133262    Patent Citation 2: Patent H11-155129